Method of making a motor protector

ABSTRACT

A HERMETICALLY-SEALED, PRESSURE-RESISTANT MOTOR PROTECTOR IS SHOWN TO COMPRISE A HEADER PLATE HAVING A TERMINAL POST ATTACHED THERETO IN INSULATING RELATION TO THE PLATE, A CUP-SHAPED BODY HAVING ITS RIM SEALED TO THE HEADER PLATE, A RIGID ANGLE-SHAPED HEATER ELEMENT, A RIGID ANGLE-SHAPED CONTACT ARM HAVING A FIXED CONTACT THEREON, AND A THERMALLY-RESPONSIVE SNAP-ACTING MEMBER HAVING A MOVABLE CONTACT AT ONE END AND HAVING AN ANGLE-SHAPED SUPPORT WELDED TO THE OPPOSITE END OF THE SNAP-ACTING MEMBER. THESE PROTECTOR COMPONENTS ARE SECURED TOGETHER BY WELDING TO PROVIDE A CIRCUIT FROM THE HEADER PLATE THROUGH THE HEATER AND SNAP-ACTING MEMBER WITH ITS MOVABLE CONTACT TO THE FIXED CONTACT AND FROM THE FIXED CONTACT THROUGH THE CONTACT ARM TO THE TERMINAL POST. THE SNAP-ACTING MEMBER IS ADAPTED TO MOVE IN RESPONSE TO HEAT GENERATED BY THE HEATER ELEMENT TO OPEN THIS CIRCUIT WHEN AN OVERLOAD CURRENT OCCURS IN THE CIRCUIT. EACH OF THE ANGLE-SHAPED COMPONENTS HAS A FIRST PORTION DISPOSED IN A SELECTED PLANE AND HAS AN ANGULARLY DISPOSED PORTION WELDED TO AN ADJACENT COMPONENT. IN THIS WAY, ANY COLLAPSE OF THE COMPONENT MATERIALS WHICH OCCURS DURING WELDING DOES NOT ALTER THE DISPOSITION OF THE FIRST PORTION OF THE RESPECTIVE COMPONENT IN ITS DESIRED PLANE. THIS PERMITS THE COMPONENTS TO BE ACCURATELY ASSEMBLED AND SECURED TOGETHER TO PROVIDE AN ACCURATE MOTOR PROTECTOR. PREFERABLY THE ANGLE-SHAPED SUPPORT COMPONENT HAS ONE FLANGE WELDED TO THE THERMALLY-RESPONSIVE SNAP-ACTING MEMBER BEFORE THE MEMBER IS DEFORMED TO PROVIDE THE MEMBER WITH ITS THERMAL RESPONSE CHARACTERISTICS. SUBSEQUENT WELDING OF THE OTHER FLANGE OF THE SUPPORT TO AN ADJACENT COMPONENT PERMITS ACCURATE MOUNTING OF THE SNAP-ACTING MEMBER IN THE MOTOR PROTECTOR WITHOUT SUBJECTING THE SNAP-ACTING MEMBER TO WELDING FORCES AND TEMPERATURES WHICH MIGHT ALTER ITS THERMAL RESPONSE CHARACTERISTICS.

NOV. 23, 1971 D'ENTREMQNT ETAL 3,621,568

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METHOD OF MAKING A MOTOR PROTECTOR Original Filed April .12, 1968 12Shouts-$11001, I7,

United States Patent M 3,621,568 METHOD OF MAKING A MOTOR PROTECTOR JohnR. DEntremont, Foxboro, and Leith B. Young,

Attleboro, Mass., assignors to Texas Instruments Incorporated, Dallas,Tex.

Original application Apr. 12, 1968, Ser. No. 720,980, now Patent No.3,538,478, dated Nov. 3, 1970. Divided and this application Jan. 26,1970, Ser. No. 10,703.

Int. Cl. H01h 11/00 US. Cl. 29-622 2 Claims ABSTRACT OF THE DISCLOSURE Ahermetically-sealed, pressure-resistant motor protector is shown tocomprise a header plate having a terminal post attached thereto ininsulated relation to the plate, a cup-shaped body having its rim sealedto the header plate, a rigid angle-shaped heater element, a rigidangle-shaped contact arm having a fixed contact thereon, and athermally-responsive snap-acting member having a movable contact at oneend and having an angle-shaped support welded to the opposite end of thesnap-acting member. These protector components are secured together bywelding to provide a circuit from the header plate through the heaterand snap-acting member with its movable contact to the fixed contact andfrom the fixed contact through the contact arm to the terminal post. Thesnap acting member is adapted to move in response to heat generated bythe heater element to open this circuit when an overload current occursin the circuit. Each of the angle-shaped components has a first portiondisposed in a selected plane and has an angularly disposed portionwelded to an adjacent component. In this way, any collapse of thecomponent materials which occurs during welding does not alter thedisposition of the first portion of the respective component in itsdesired plane. This permits the components to be accurately assembledand secured together to provide an accurate motor protector. Preferablythe angle-shaped support component has one flange welded to thethermally-responsive snap-acting member before the member is deformed toprovide the member with its thermal response characteristics. Subsequentwelding of the other flange of the support to an adjacent componentpermits accurate mounting of the snap-acting member in the motorprotector without subjecting the snap-acting member to welding forcesand temperatures which might alter its thermal response characteristics.

This is a division of our application Ser. No. 720,980, filed Apr. 12,1968 and now Pat. No. 3,538,478.

Small sealed motor protector devices having snap-act ing,thermally-responsive members are most economically manufactured bysecuring the device parts together by means of welding. However, the useof conventional welding techniques in manufacturing such devicesfrequently exposes the device components to excessive forces andtemperatures which cause uncontrollable changes in the thermal responsecharacteristics of the snap-acting device members. Further, even thoughdevice parts are initially located in the proper relationship to eachother prior to welding, collapse of the part material in the areas beingwelded, and spring-back of the parts after completion of welding, tendto alter the part spacings so that the thermal response characteristicsof the resulting devices are not uniform and so that many of the devicesare not acceptable for their intended purpose.

It is an object of this invention to provide a novel and improved motorprotector device; to provide such a motor protector which ishermetically sealed and pressure resistant; to provide such a motorprotector which has Patented Nov. 23, 1971 accurately predeterminedthermal response characteristics; and to provide such a motor protectorwhich is of simple, rugged and economical construction. It is a furtherobject of this invention to provide a novel and improved method forconveniently and accurately manufacturing such motor protector deviceswith uniform thermal response charactertistics. A

Other objects, advantages and details of the motor protector devise andmethod of this invention appear in the following detailed description ofpreferred embodiments of this invention, the detailed descriptionreferring to the drawings in which:

FIG. 1 is a section view along the longitudinal axis of the motorprotector device of this invention;

FIG. 2 is a section view along line 2-2 of FIG. 1;

FIG. 3 is a section view along line 33 of FIG. 2;

FIG. 4 is a side elevation view of components of the device of FIG. 1illustrating a step in the manufacture of th] device;

FIG. 5 is a side elevation view of device components similar to FIG. 4illustrating a subsequent step in the method of this invention; and

FIG. 6 is a side elevation view of device components similar to FIGS. 4and 5 illustrating a further step in the method of this invention.

Referring to the drawings, 10 in FIGS. 1-3 indicates the novel andimproved motor protector of this invention which is shown to include agenerally disc-shaped header plate or member 12 having a centralaperture 14 and having a terminal post 16 secured in the plate aperturein insulated relation to the plate by means of a sealant material 18.The header plate and terminal post are prefferably formed of a rigid,electrically conductive material such as steel or the like. The rod ismounted in sealed, electrically insulated relation to the header plateby use of a glass sealant material 18 or other conventional electricallyinsulating material. As the terminal post is mounted in the header platein the described manner by any well known technique, sealing of theterminal post and the header plate is not further described herein.

As shown, the motor protector 10 further includes a rigid electricallyconductive contact arm 20 formed of steel or the like, the arm includingone flange portion 22 which is welded to one side of the terminal post16 as indicated at 24 in FIG. 2 and including an angularly disposedflange portion 26 which extends in cantilever relation from the post 16in a plane generally parallel to the terminal post 16. A fixed contact30, preferably formed of material of high electrical conductivity suchas silver, is welded or otherwise secured to the distal end of theextending portion of the contact arm as shown.

The motor protector 10 further includes a heater element or member 32having one flange portion 34 welded to the header plate 12 as indicatedat 35 and having a second flange 36 extending in cantilever relationfrom the header plate so that an edge 37 of the extending flange facesthe terminal post 16. The heater element preferably includes a stop orend portion 38 which terminates in a plane lying parallel to the axis ofthe terminal post 16. The heater element also preferably has a roundedsurface 39 formed on the edge 37 of the flange 36 as shown in FIG. 2.The heater element is formed of any one of a variety of materials ofselected electrical conductivity so that the element is adapted togenerate a predetermined amount of heat in response to selected flow ofelectrical current through the element. For example, the heater elementis preferably formed of rigid cold-rolled steel to provide the elementwith selected electrical heating characteristics. Alternately, heaterelements of other rigid metals or the like are used for providing theheater with different electrical heating properties within the scope ofthis invention.

In addition, the motor protector includes an electrically conductive,angle-shaped support 42 of cold-rolled steel or the like which has oneflange 44 welded to the heater element flange 36 as indicated at 46 inFIG. 2 and another flange 48 welded to an electrically conductive,resilient, thermally-responsive snap-acting member 50 as indicated at 52in FIG. 1. A movable contact 54, preferably formed of the same materialas the fixed contact 30, is welded or otherwise secured to thethermallyresponsive member oppositely of the support 42. As illustrated,the flange portion 44 of the support extends away from thethermally-responsive member at substantially a right angle to thegeneral plane of the member. The welding of the support 42 to the heater32 disposes the thermally-responsive member 50 in selected heat-transferrelation to the heater element and locates the member 50 extending incantilever relation from the heater so that the movable contact 54engages and disengages the fixed contact 30 in response to snap-actingmovement of the member 50. That is, the member 50 is normally located asillustrated in solid lines in FIG. 2 so that the member resilientlyholds the movable contact in engagement with the fixed contact to closea circuit from the header plate 12 through the heater 32, support 42,snap-acting member 50, contacts 54 and 30, and contact arm 20 to theterminal post 16. When this motor protector circuit is interposed in anelectrical motor circuit, current flow through the heater element 32ofthe motor protector does not normally generate suflicient heat tocause movement of the thermally-responsive member 50 so that the motorprotector circuit remains closed. However, when abnormal current flowsin the motor circuit, increased current flow through the heater element32 generates sufficient heat to cause the snap-acting member 50 to movewith snapaction to the position indicated by dotted lines 50.1 in FIG. 2to disengage the contacts 54 and 30 and to open the described motorprotector circuit. In this open circuit position, the snap-acting member50 resiliently engages stop portion 38 of the heater element forlimiting travel of the member away from the fixed contact and for preventing undesirable movement of the member in response to vibration andthe like.

A cup-shaped body 56 formed of steel or other rigid material has its rimwelded in electrically conductive relation to the header plate 16 asindicated at 58 to form a device chamber 59, this weld serving to sealthe device chamber so that the motor protector 10 is completely sealedand pressure resistant. Preferably, the body has a flat portion 61 shownin FIG. 3 for use in locating the device 10 when mounting the device ina motor circuit.

In accordance with the method of this invention, the terminal post '16is mounted in sealed insulated relation within the header plate aperturein conventional manner as shown. The heater element 32 is then locatedwith the outer surface of the flange 34 engaged with the header plate,with the edge 37 of the heater facing toward the terminal post, and withthe end of the stop portion 38 disposed in a plane properly spaced atthe distance a from the plane of the terminal post axis as indicated inFIG. 2. The heater element is then welded to the header plate asindicated at 35. Any collapse of the header plate or heater materialoccurring during formation of the weld at 35, and any spring back of theheater flanges after completion of the weld at 35, does not alter thespacing a used in locating the end of the stop 38 in the proper plane.That is, the welding of the heater is easily accomplished to dispose thestop in the proper plane even though the relative angular disposition ofthe heater element flanges may be other than as desired.

In accordance with the method of this invention, thethermally-responsive snap-acting element 50 is formed from astrip-shaped blank 50.2 of bimetallic material as illustrated in FIG. 4.That is, the strip 50.2 embodies two layers of metal bonded together,the metals being characterized by relatively high and low coeflicientsof thermal expansion respectively so that the strip tends to flex inresponse to temperature change. The movable device contact 54 is weldedor otherwise secured to one end of the strip. In addition, one flange 48of the support 42 is welded at 52 -to the opposite end of the strip withthe support flange 44 extending out of the general plane of the strip,this flange preferably having weld projections 46.1 thereon as shown inFIG. 4. After securing of the contact and support to the strip, thestrip is deformed in conventional manner as shown in FIG. 5 to provide adished-shaped portion 60 intermediate the support and contact, therebyto form a snap-acting member 50 of selected thermal responsecharacteristics. As methods for deforming such bimetallic materials toform thermallyresponsive snap-acting elements having preciselycontrolled thermal response characteristics are well known, thedeformation of the strip 50.2 is not further described herein and itwill be understood that the deformation is performed after welding ofthe support and contact to the strip within the scope of this invention.

In the method of this inveniton, the snap-acting member 50 with itsattached support and contact is located with the flange 44 of thesupport engaging the flange 36 of the heater element and with themovable contact 54 aligned with and located in a plane at a distance 0from the stop 38 of the heater element as shown in FIG. 6. In locatingthe fixed contact at the desired spacing from the heater stop, thesupport flange 44 is conveniently engaged with the rounded surface 39 ofthe heater element and is moved against this rounded surface to aid inlocating the contact in the desired relation to the heater element stop.The support flange 44 and the flange 36 of the heater are then weldedtogether at 46 as by gripping the support and heater flanges between theelectrodes of a conventional resistance welding machine (not shown) orin other conventional manner. Note that, because the support flange 44extends out of the general plane of the thermally-responsive member 50,no significant part of the heat normally generated during welding willbe directed through the bimetallic member and the thermal responsivecharacteristics of the member will not be altered during the welding. Inaddition, although it will be understood that some collapsing of theheater and support material will tend to occur in the area where thisweld is formed, this collapsing of the material does not alter thespacing 0 between the plane of the heater element stop and the contact54. Thus the use of the support 42 permits the bimetallic member andheater element to be accurately secured together while retaining thedesired thermal response characteristics of the bimetallic member.

In the method of this invention, the fixed contact 30 is welded orotherwise secured to the contact arm 20 and the arm flange 22 is engagedwith one side of the thermal post 16 so that the contact 30 is disposedin a plane at a selected distance d from the stop 38 and in selectedrelationship to the movable contact 54. The engaging portions of thecontact arm and terminal post are then welded together as indicated at24 to maintain the fixed and movable contacts in the desiredrelationship. Again, any collapse of the contact arm or terminal postmaterial in the area of the weld 24 does not alter location of the fixedcontact in its desired plane. Further, even though the relative angulardisposition of the contact arm flanges is other than as desired, thecontact 50 is easily located in the desired plane. The cup-shaped body56 is then welded to the header plate to complete assembly of the motorprotector 10.

In this way, the motor protector is economically constructed to displayprecisely predetermined thermal response properties. The device isrugged and inexpensive, is hermetically sealed and pressure-resistant,is vibrationresistant so that the device does not tend to open or closea circuit inadvertently even when exposed to substantial vibrationalforces, and is particularly suited for use in a freon atmosphere or thelike to protect motors of various types.

It should be understood that although particular embodiments of themotor protector and method of this invention have been described by wayof illustration, modifications of structure could be made Within thescope of this invention. For example, the heater element and contact armconfigurations could be interchanged, the heater then being welded tothe terminal post and the contact arm being welded to the header plate.This invention includes all modifications and equivalents of theillustrated embodiments of the inventions which fall within the scope ofthe appended claims.

We claim:

'1. A method for making a motor protector comprising the steps ofproviding an electrically-conductive header plate having a terminalmounted in sealed, electrically insulated relation to said plate,welding one flange of a rigid angle-shaped contact arm to said terminalso that said arm extends in cantilever relation therefrom, said armhaving a fixed contact mounted at the distal end of said arm, weldingone flange of a rigid angle-shaped heater element to said plate so thatsaid heater element extends in cantilever relation from said plate inselected relation to said fixed contact, welding anelectrically-conductive movable contact to one end of a strip-shapedbimetallic blank, welding one flange of an angle-shaped support to anopposite end of said blank so that another support flange extends out ofthe general plane of said blank, deforming said blank to provide athermally-responsive snapacting member having selected thermal responsecharacteristics, and welding said extending flange of said support tosaid heater element to dispose said movable contact to engage anddisengage said fixed contact in response to snap-acting movement of saidthermally-responsive member.

2. The method as set forth in claim 1 wherein an openended cup-shapedrigid body is welded at its rim in sealed relation to said header platefor enclosing said heater element, contact arm and thermally-responsivemember.

References Cited UNITED STATES PATENTS 3,242,292 3/1966 Malone 337-112 X3,361,883 1/1968 Brassard et a1 29622 X 3,431,526 4/1969 Ambler et a133789 JOHN F. CAMPBELL, Primary Examiner C. E. HALL, Assistant ExaminerU.S. Cl. X.R.

